/*
 *  Copyright 2013 National Institute of Advanced Industrial Science and Technology
 *  
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *  
 *      http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.sss.common.io;

import java.io.IOException;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.sss.common.DataReceiver;
import org.sss.common.KeyValues;
import org.sss.mapreduce.Configuration;
import org.sss.mapreduce.DB;
import org.sss.mapreduce.GroupID;
import org.sss.mapreduce.SssException;
import org.sss.mapreduce.StorageNode;

public class RestrictedRawKeyFirstKeyValueReader extends AbstractKeyValueReader {
  private static Logger logger = LoggerFactory.getLogger(RestrictedRawKeyFirstKeyValueReader.class);

  public RestrictedRawKeyFirstKeyValueReader(Configuration conf,
                                              StorageNode node,
                                              GroupID source,
                                              int subhash,
                                              DataReceiver<List<KeyValues>> next) throws SssException {
    super(conf, node, source, subhash, next);
  }

  @Override
  protected void doRead(IOThread iot)
    throws SssException, IOException, InterruptedException {
    assert getSource() != null: "source should not be null";
    DB db = iot.getDB(node);
    int count_max = iot.getIOGetBatchCount();
    int limitNBytes = iot.getIOGetLimitNBytes();

    final KeyFormatter keyFormatter = KeyFormatter.get(getSource().getKeyFormat());
    assert keyFormatter == KeyFormatter.userKeyPriorityFormatter: "KeyFormatter is not userKeyPriorityFormatter.";
    byte[] prefix = KeyFormatter.getPrefix(getSource(), subhash);
    final List<byte[]> allkeys = db.fwmkeys(prefix, -1);
    final int count_target = allkeys.size();
    boolean done = count_target == 0;
    int count_sofar = 0;
    byte[] key = null;

    KeyValuesQueue kvq = new KeyValuesQueue(next, limitNBytes);
    try {
      while (!done) {
        checkCanceled();
        final int count_tmp = Math.min(count_target - count_sofar, count_max);
        byte[][] ks = new byte[count_tmp][];
        for (int i=0; i<count_tmp; i++) {
          ks[i] = allkeys.get(count_sofar + i);
          allkeys.set(count_sofar + i, null); // for gc
        }
        List<byte[]> kvs = db.getlist(ks);
        countup(kvs);
        final int count_read = kvs.size();
        logger.debug("count_read = {}", count_read);
        count_sofar += count_read / 2;
        if (isDestructiveRead() && count_read > 0) {
          db.outlist(ks);
        }
        done = count_target == count_sofar;
        for (int i=0; i<count_read; i+=2) {
          if (key == null || !keyFormatter.rawKeyEquals(kvs.get(i), key)) {
            key = keyFormatter.getUserKey(kvs.get(i));
            kvq.pushKey(key);
          }
          kvq.pushValue(kvs.get(i + 1));
        }
      }
    }
    finally {
      kvq.pushEnd();
    }
  }
}
